Light pipe for accurate erasure of photoconductor charge

Abstract

Erase apparatus for use in an electrophotographic copier machine where an array of light-emitting diodes (LEDs) are placed adjacent one end of a light channel with the other end adjacent a moving photoreceptive surface. The channel allows light rays to pass freely from LED to LED but contains the rays in a direction parallel to the direction of photoreceptor movement. The channel may be comprised of sides with reflective surfaces normal to the photoreceptive surface or may be a solid plastic sheet through which the rays pass. In the latter embodiment, rays are internally reflected from the surfaces of the plastic sheet.

What is claimed is: 
     
       1. An electrophotographic copier machine wherein a photoreceptive surface is charged to receive an image within an image area of specified size, comprising: means upon which said photoreceptive surface is mounted for moving said surface in a continuous path;   charge-generating means located along said path for producing a relatively uniform electrostatic charge on said surface;   exposing means for directing light rays from an object to said surface to produce a variable discharge of said image area such that said image area is caused to bear an electrostatic image of said object;   developing means to develop said electrostatic image by depositing developing material on said surface;   transfer means to transfer the developed image to a copy-receiving medium;   cleaning means to clean said surface of excess developing material to prepare said surface for producing a subsequent copy;   first charge erase means located along said path between said charge-generating means and said developing means for removing charge on said surface between image areas, said first means comprising an array of light-emitting diodes;   second charge erase means also located along said path between said charge-generating means and said developing means for removing charge along the edges of said surface outside said image area, said second means comprising an array of light-emitting diodes; and   light channel means comprising a plurality of sheets of transparent material located between said array of light-emitting diodes (LED) and said surface, for allowing light rays to propagate freely in a first direction parallel to said surface from LED to LED within each one of said plurality of sheets, said sheets separated from each other by an air space to divide said array into groups of LEDs, said sheets having sides essentially normal to said surface so as to contain said light rays between said sides in a second direction normal to said first direction.   
     
     
       2. The machine of claim 1 wherein said groups of LEDs are individually controlled. 
     
     
       3. In an electrophotographic machine of the transfer type wherein erase mechanisms are included for shaping the charged image area of a moving photoreceptive surface to the dimensions of the image, the improvements comprising: an array of LEDs for producing light rays to erase charge outside of said image area, said array located adjacent to said surface across the width thereof;   a light channel means located between said array and said surface to freely propagate said light rays in a first direction parallel to said surface from LED to LED while containing said light rays in a second direction normal to said first direction and   said light channel means comprising a plurality of sheets of transparent material located between said array of LEDs and said surface, each one of said sheets separated from the other by an air gap to divide said array into groups of LEDs.   
     
     
       4. The machine of claim 3 wherein said groups of LEDs are individually controlled.